Hemodialysis is a water intensive therapy that presents an enormous challenge to cost effectively produce very large amounts of high purity water. The occurrence of bacteria and endotoxins in dialysis fluids is traced to biofilm that grows at surfaces in contact with water in dialysis water systems. Current liquid circulation maintenance methods are not capable of removing biofilm from dialysis water systems, and thus are incapable of eliminating the main source of biological contamination of dialysis water. Such methods are tedious, labor-intensive, time-consuming and costly. We propose to use a two-phase flow cleaning technology proven to remove biofilm from long and narrow passageways to eradicate biofilm and control its proliferation in dialysis water systems. The specific aims of the study are: 1) To define and build a simulated dialysis unit water system mimicking an actual water system at a dialysis clinic; 2) To define flow and fluid dynamics parameters of the two-phase flow process necessary to remove biofilm from pipelines of dialysis unit water systems; 3) To optimize and validate the two-phase cleaning/disinfection process protocol for a dialysis unit water system using standard microbiology methods; and 4) To define system requirements to be applied at the dialysis units in the clinical setting during the Phase II study. The Phase I study will focus on cleaning and eradicating biofilm from RO water and bicarbonate solution loops of the water system. This approach presents a cardinal new means of producing and maintaining high quality water for use in hemodialysis treatment.